Abstract：The two-phase performance difference of ferrite and martensite in dual-phase steel,caused the welded joint to soften. When the using temperature was low, the impact energy decreased,caused the material change from a ductile state to a brittle state. In order to research the Ce and Nb addition on the brittleness with low temperature improvement of DP780 weld,used low temperature impact test and tensile test,to study mechanical properties of DP780 weld with different Ce and Nb addition. Used metallographic microscope,SEM and other methods, clarified the changes in weld microstructure and morphology which added different Ce and Nb. The results showed that at -40 ℃,residual austenite appeared in the microstructure without Ce and Nb,the impact energy of the weld was 0.465 J. And a large number of river patterns appeared on the cleavage step surface,which belonged to brittle fracture. As the Ce and Nb mass percents changed,the impact energy of the weld was nonlinear with Ce and Nb addition. When the mass percent of Ce and Nb was 0.35% and 0.15% of the deposited metal,the weld had the best overall performance,the impact energy of the weld reached to 3.9 J. The deposited metal structure had dense grain boundaries,and dimples appeared around the tearing edge,showed mix fracture characteristics. It appeared that add appropriate amount of Ce and Nb,rare earth compounded form in welds,could increase the fracture deformation resistance and energy consumption. Thereby effectively retard the crack propagation,significantly improved the low-temperature impact toughness of DP780,and would not greatly reduce its tensile strength,ensured the welding quality of dual-phase steel. But there was no fixed function relationship between Ce and Nb on weld performance,and the sample size was small,could not be accurate to any addition amount. In the follow-up research,algorithms could be introduce to predict the mechanical properties of DP780 welds,build the model before production,to find the best addition of cerium and niobium,improved safety performance.
赵瑾玥, 郭永环, 闫勃. 铈和铌改性对DP780双相钢焊缝冲击性能的影响[J]. 钢铁, 2021, 56(11): 135-140.
ZHAO Jin-yue, GUO Yong-huan, YAN Bo. Effect of Ce and Nb modification on weld impact properties of DP780 duplex steel[J]. Iron and Steel, 2021, 56(11): 135-140.
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2021, Vol. 56 
